Patent Application
20100047673
The present invention relates to a battery pack accommodating a battery having a risk of releasing a gas under abnormal conditions and to a battery-mounted device.
Recently, in association with diversification of electronic devices, a need for high-capacity, high-voltage, high-power, and safer battery and battery pack is increasing. In order to provide a battery and a battery pack with particularly high safety, there has been known a technique for providing a battery and a battery pack with various types of protection means, such as a PTC (Positive Temperature Coefficient) or a temperature fuse to prevent a temperature rise, and further a protection circuit to interrupt a current by sensing an internal pressure of the battery. A technique for providing a battery pack with a control circuit that controls charge and discharge of a battery for preventing the battery from being placed under abnormal conditions has been also known.
However, even when the protection means and the control circuit as described above are provided, the battery has a possibility of ejecting an inflammable gas from inside the battery when placed under abnormal conditions. Should such an event happen, it is probable that the case accommodating the battery breaks, melts or burns, or the ejected inflammable gas leaks to the outside of the battery pack or the ejected inflammable gas burns and fire spreads inside and outside the battery pack, which results in further damage.
As a method of preventing such phenomena, there have been proposed a method (see, for example, Patent Document 1) for a battery pack formed of a case accommodating a plurality of batteries, by which a gas released from a battery is released to the outside of the case while being diffused within the case so as to lower the temperature and the pressure, and a method (see, for example, Patent Document 2), by which a bag that takes on a duct-like shape when inflated is attached to a group of electric cells formed by aligning and interconnecting a plurality of batteries each having a safety valve for releasing a gas when an internal pressure of the battery rises to or above a predetermined value, so that the bag inflates and forms a duct when a huge volume of gas is produced for discharging a gas released from the battery to the outside and thereby lowering the pressure of the discharged gas.
However, because the gas discharged from a battery has a high temperature and pressure gas and highly inflammable, there is a risk of ignition upon contact or mixture with oxygen in air. In addition, because the batteries and the case accommodating the batteries are, for example, of shapes different from each other, a space is left between the batteries and the inner wall of the case. In some instances, a space is provided between the batteries and the inner wall of the case in order to accommodate wires interconnecting a plurality of batteries, a protection element to safeguard the batteries against an overcurrent or an overvoltage, and the like. The space within the case is filled with air and oxygen is contained in air.
Under these circumstances, even when an inflammable gas discharged from a battery is released to the outside while being diffused within the case of the battery pack according to the technique described in Patent Document 1, the presence of a space within the case poses a risk that the inflammable gas ignites by reacting with oxygen in air within the case, which gives rise to combustion of the flammable gas within the entire case, resulting in damage on more than one battery. Also, even when an inflammable gas released from a battery is discharged to the outside via the duct according to the technique described in Patent Document 2, there is a risk that the inflammable gas ignites by reacting with air within the duct and gives damage on the duct to the extent that the inflammable gas leaks inside the case and the inflammable gas in turn ignites by reacting with oxygen in air within the case, which gives rise to combustion of the inflammable gas within the entire case, resulting in damage on more than one battery.
Patent Document 1: JP-A-2005-322434
Patent Document 2: JP-A-2005-339932
The invention is achieved in view of the foregoing problems, and it is therefore an object of the present invention to provide a battery pack and a battery-mounted device capable of lowering a risk of damage caused by combustion of a gas even when the gas is released from a battery.
A battery pack according to one aspect of the present invention includes a battery having a risk of releasing a gas under abnormal conditions, a case that accommodates the battery, and an oxygen reducing portion that reduces an amount of oxygen within the case.
According to the foregoing structure, an amount of oxygen within the case is reduced by the oxygen reducing portion. Hence, should a gas be released from the battery, it is possible to lessen damage on the battery pack caused by combustion of the gas within the case because an amount of oxygen to react with the gas has been reduced.
Also, a battery-mounted device according to still another aspect of the invention includes a battery having a risk of releasing a gas under abnormal conditions, an accommodation chamber that accommodates the battery, and an oxygen reducing portion that reduces an amount of oxygen within the accommodation chamber.
According to the foregoing structure, an amount of oxygen within the accommodation chamber in which is accommodated the battery having a risk of releasing a gas is reduced by the oxygen reducing portion incorporated in the battery-mounted device. Hence, should a gas be released from the battery, it is possible to lower a risk that the battery and the battery-mounted device are damaged by combustion of the gas within the accommodation chamber because an amount of oxygen to react with the gas has been reduced.
Hereinafter, embodiments of the invention will be described on the basis of the drawings.
The battery pack 1 shown in
As is shown in
A groove 313 of an almost circular shape is formed in the sealing plate 310 almost at the center. It is configured in such a manner that the groove 313 breaks when an internal pressure of the case 308 exceeds a predetermined pressure due to a gas generated inside, so that the gas within the case 308 is released. A convex portion for external connection is provided to the positive electrode 311 at almost the center and the convex portion is provided with an electrode opening 314 (releasing hole). It is therefore configured in such a manner that the gas released when the groove 313 breaks is released to the outside of the battery 3 through the electrode opening 314.
Forming the battery 3 by spirally winding the pole plate group 312 as is shown in
Meanwhile, the battery pack 1 is used in a state where it is accommodated in the case of a battery-mounted device or attached to the outer wall of the battery-mounted device. It is therefore general to form the case 2 in a rectangular box shape so that it can be readily accommodated into or attached to the device case. Consequently, the battery 3 is of a cylindrical shape whereas the case 2 is of a rectangular shape. Hence, when the cylindrical battery 3 is accommodated in the rectangular case 2, a space is left between the battery 3 and the inner wall of the case 2 due to the difference in shape, which increases an amount of oxygen within the case 2 unless some measure is taken. It should be noted, however, that the battery pack 1 shown in
It is configured in such a manner that the opening 23 is clogged by the pressure-actuated valve 52 when the pressure-actuated valve 52 is pressed against the opening 23 by the pressure-actuated spring 53. With this structure, it is possible to prevent air from flowing inside the case from the outside.
When the internal pressure of the case 2 rises above the pressure at which the pressure-actuated valve 52 is pressed against the opening 23 by the pressure-actuated spring 53, the pressure-actuated valve 52 starts to move by pushing the pressure-actuated spring 53 under compression. A ventilation channel from the opening 23 to the opening 54 is thus defined and a gas within the case 2 is released through the opening 23 and the opening 54.
The battery pack 1 formed as described above is able to lessen damage on the battery pack 1 caused by combustion of a gas by suppressing combustion of the gas even when the gas is ejected from inside a battery 3 due to heat generation of the battery 3 caused by internal short-circuit or overcharge, because an amount of oxygen present within the case 2 has been reduced by the filling members 4.
Also, in a case where the pressure of a gas within the case 2 exceeds the operating pressure of the pressure valve 5, the pressure valve 5 opens to release the gas. The internal pressure of the case 2 can be thus lowered, and so is the risk that the case 2 explodes due to the pressure of the gas released from the battery 3. In addition, the opening 23 is kept clogged by the pressure valve 5 until the pressure of the gas within the case 2 exceeds the operating pressure of the pressure valve 5. It thus becomes possible to prevent air form flowing inside the case 2 from the outside through the opening 23. Consequently, a supply of new oxygen inside the case 2 from the outside is suppressed, which suppresses combustion of the gas. It thus becomes possible to lessen damage on the battery pack 1 caused by combustion of the gas.
Regarding the filling members 4, a case where a solid material is attached to the inner wall of the case 2 has been described. They are, however, not necessarily attached to the case 2. It is sufficient to dispose the filling members 4 so as to reduce the space within the case 2. Alternatively, they may be formed integrally with the case 2.
Also, regarding the filling members 4, a case where they are provided to fill a clearance generated due to the difference in shape between the cylindrical batteries 3 and the almost rectangular box-shaped case 2 has been described. However, as are shown in
By disposing a plurality of the batteries 3 inside the case 2 in close adhesion to each other, a clearance can be lessened further, which makes it possible to reduce more oxygen within the case 2. However, in order to dispose, for example, the connection plates 32 between the respective batteries 3, or unillustrated protection elements to safeguard, for example, the batteries 3 against an overcurrent or an overvoltage and unillustrated wires to detect output voltages of the batteries 3, there is a case where it is necessary to provide an interval t between the adjacent batteries 3 as is shown in
Also, a material of the filling members 4 is not limited as long as the material is able to reduce an amount of oxygen present within the case 2 by reducing the space within the case 2. Examples of available materials include but not limited to nonflammable solids including metal, such as aluminum and titanium, ceramic, and sand, nonflammable liquids including water and ionic liquids based on imidazolium salt, pyridinium salt, and aliphatic quaternary ammonium salt, nonflammable gases, such as argon, nitrogen, and carbon dioxide, and nonflammable adiabatic agents, such as HEAT BUSTER TK2 available from Kabushiki Kaisha PDM Kenkyuusho.
In a case where nonflammable materials as specified above are used as the filling members 4, even when a battery 3 generates heat due to internal short-circuit or overcharge or a slight amount of oxygen remaining within the case 2 slightly burns (undergoes incomplete combustion) by reacting with a gas released from the battery 3, the filling members 4 remain unburned. It is therefore possible to suppress an increase in damage on the battery pack 1.
In a case where liquid or gaseous materials are used as the filling members 4, these nonflammable materials may be encapsulated in a container that readily melts with heat, for example, a bag made of polypropylene, so that the noninflammable material encapsulated in the bag is used as the filling members 4. Also, in a case where liquid materials are used as the filling materials 4, these materials may be absorbed, for example, into high-polymer materials, so that they are filled in the space as a gel-like material.
Also, for example, as is shown in
In addition an oxygen absorbing member that absorbs oxygen, for example, oxygen absorbing members including iron (II) sulfate, activated carbon, or AGELESS (registered trademark) available from Mitsubishi Gas Chemical Company, Inc., may be used as the filling members 4 as well. In this case, because an amount of oxygen present within the case 2 is reduced by the oxygen absorbing member, even when an inflammable gas is ejected from a battery 3, combustion of the gas can be suppressed. It thus becomes possible to lessen damage on the battery pack 1 caused by combustion of the gas.
Also, an inert gas releasing member that releases an inert gas when the temperature exceeds a predetermined temperature may be used as the filling members 4. Examples of such an inert gas releasing member include but not limited to sodium hydrogen carbonate and magnesium carbonate that release carbon dioxide when overheated. In this case, when the temperature of the filling members 4 rises as a battery 3 generates heat due to internal short-circuit or overcharge or a slight amount of oxygen remaining within the case 2 slightly burns (undergoes incomplete combustion) by reacting with a gas released from the battery 3, the filling members 4 releases an inert gas, which forces air within the case 2 out to be discharged through the opening 23 and the pressure valve 5. Accordingly, an amount of oxygen present within the case 2 is reduced and combustion of the gas released from the battery 3 is suppressed. It thus becomes possible to lessen damage on the battery pack 1 caused by combustion of the gas.
The filling materials 4 are not necessarily provided. For example, the case 2 may be formed using an oxygen absorbing member or an inert gas releasing member by kneading the oxygen absorbing member or the inert gas releasing material into a raw material of the case 2. Accordingly, oxygen present within the case 2 is reduced by the case 2 and combustion of a gas released from a battery 3 is suppressed. It thus becomes possible to lessen damage on the battery pack 1 caused by combustion of the gas.
Also, as is shown in
In this case, when the internal pressure of a battery 3 rises and a gas is released through the electrode opening 314, the released gas is guided to the opening 23 and released to the outside through the pressure valve 5. Accordingly, combustion of the gas released through the electrode opening 314 that is triggered by a reaction with oxygen present on the periphery of the battery 3 can be suppressed. It thus becomes possible to lessen damage on the battery pack 1.
The pressure valve 5 is not necessarily provided, either. For example, the hole diameter of the opening 23 may be made smaller to make it difficult for outside air to flow inside the case 2. Besides the foregoing, it is possible to adopt various configurations as the pressure valve 5. For example, an annular groove may be formed in the wall surface of the case 2, so that the annular groove functions as a pressure valve by breaking when an internal pressure of the case 2 rises.
Alternatively, inflow prevention portions 5a, 5b, and 5c as shown, for example, in
The inflow prevention portion 5c shown in
The sectional area of the tube at the inflow prevention portions 5a, 5b, and 5c is determined by a capacity per cell of the batteries 3 disposed inside the case 2. As a rough indication, when a capacity of the battery 3 is about 2 Ah, the sectional area is preferably 16 mm2 or larger, when a capacity is about 5 Ah, the sectional area is preferably 40 mm2 or larger, and when the capacity is about 10 Ah, the sectional area is about 80 mm2 or larger. In this case, a preferable material of the tube is metal, such as copper, aluminum, and stainless by taking heat releasing performance and heat resistance into account. Also, the inflow prevention portion 5a, 5b, or 5c may be attached to the electrode opening 314 of each battery 3.
A case where the battery pack 1 accommodates a plurality of the cylindrical batteries 3 in the case 2 has been described. It should be appreciated that the shape of the batteries 3 is not limited to a cylindrical shape and only a single battery 3 may be accommodated in the case 2. In a case where a plurality of batteries 3 are accommodated in the case 2, the battery pack 1 is able to suppress combustion of a gas within the case 2 even when any one of the batteries 3 generates heat due to internal short-circuit or overcharge and a gas is released from this battery 3. It is therefore possible to lessen damage on the batteries 3 other than the battery 3 that has released the gas.
Also, a case where the batteries 3 aligned in a single line are accommodated in the case 2 has been described. However, for example, as is shown in
Also, a material filling a space within the case 2 is not necessarily filled in the case 2 in advance. For example, a tank storing a nonflammable gas or liquid or a device that produces a nonflammable gas may be provided as an oxygen reducing portion that reduces oxygen within the case 2 by supplying the nonflammable gas or liquid inside the case 2, so that the nonflammable gas or liquid may be supplied inside the case 2 from the tank or the device periodically or when the internal temperature of the case 2 reaches or exceeds a predetermined temperature.
The oxygen reducing portion as described above is not necessarily provided as a part of the battery pack. A tank storing a nonflammable gas or liquid or a device that generates a nonflammable gas and a control device that controls a supply of the nonflammable gas or liquid to the case 2 from the tank or the device may be provided to the battery-mounted device on which the battery pack is mounted. Also, besides a battery pack having an independent case, for example, an accommodation chamber to accommodate the batteries 3 may be formed by integrally forming the battery pack with the case of the battery-mounted device, so that this accommodation chamber is used instead of the case 2.
Examples of the battery pack according to a first embodiment of the invention will be described.
The battery 3 shown in
The positive plate 301 was fabricated in the following manner. Herein, 85 parts by weight of lithium cobalt oxide powder as the positive mixture, 10 parts by weight of carbon powder as a conducting agent, and an N-methyl-2-pyrrolidone (hereinafter abbreviated as NMP) solution of polyvinylidene-fluoride (hereinafter, abbreviated as PVDF) as a binder in an amount comparable to 5 parts by weight of PVDF were mixed. The resulting mixture was applied on a 15-μm-thick aluminum foil current collector followed by drying and then rolling. The positive plate 301 having a thickness of 100 μm was thus fabricated.
The negative plate 303 was fabricated in the following manner. Herein, 95 parts by weight of artificial graphite powder as the negative mixture and an NMP solution of PVDF as a binder in an amount comparable to 5 parts by weight of PVDF were mixed. The resulting mixture was applied on a 10-μm-thick copper foil current collector followed by drying and then rolling. The negative plate 303 having a thickness of 110 μm was thus fabricated.
A nonaqueous electrolyte was prepared in the following manner. Ethylene carbonate and ethylmethyl carbonate were mixed in a volume ratio of 1:1 as a nonaqueous solvent. Lithium hexafluorophosphate (LiPF6) as a solute was dissolved in the resulting nonaqueous solvent to achieve 1 mol/L. Herein, 4.5 ml of the nonaqueous electrolyte prepared in this manner was used.
The 25-μm-thick separator 305 was disposed between the positive plate 301 and the negative plate 303 and they were wounded together to form the cylindrical pole plate group 312, which was then inserted and sealed in the metal bottomed-case 308. The nonaqueous electrolyte secondary battery 3 was thus obtained. This battery was a cylindrical battery having a diameter of 25 mm and a height of 65 mm and the designed capacity of the battery was 2000 mAh. The completed battery 3 was covered with an 80-μm-thick heat-shrinkable tube made of polyethylene terephthalate used as the battery can insulator 33 up to the outer ridge of the top face. The battery was completed when the shrinkable tube was shrunk by heat with a hot air of 90° C.
Herein, six batteries 3 formed as above, which are cylindrical lithium-ion secondary batteries, were aligned as shown in
As are shown in
A battery pack of Example 2 was fabricated by aligning the batteries 3 while leaving an interval t of 5 mm from one battery 3 to another battery 3 as are shown in
A battery pack of Example 3 was fabricated by aligning the batteries 3 while leaving an interval t of 5 mm from one battery 3 to another battery 3 as are shown in
A battery pack of Example 4 was fabricated by aligning the batteries 3 while leaving an interval t of 5 mm from one battery 3 to another battery 3 as are shown in
A battery pack of Example 5 was fabricated by aligning the batteries 3 while leaving an interval t of 5 mm from one battery 3 to another battery 3 as are shown in
A battery pack of Example 6 was formed by aligning the batteries 3 while leaving an interval t of 5 mm from one battery 3 to another battery 3 as is shown in
A battery pack of Example 7 was formed by aligning the batteries 3 while leaving an interval t of 5 mm from one battery 3 to another battery 3 as are shown in
A battery pack of Example 8 was formed by aligning the batteries 3 while leaving an interval t of 5 mm from one battery 3 to another battery 3 as is shown in
A battery pack of Example 9 was formed by aligning the batteries 3 while leaving an interval t of 5 mm from one battery 3 to another battery 3 as is shown in
A battery pack of Example 10 was formed by aligning the batteries 3 while leaving an interval t of 5 mm from one battery 3 to another battery 3 as is shown in
A battery pack of Example 11 was formed by aligning the batteries 3 while leaving an interval t of 5 mm from one battery 3 to another battery 3 as are shown in
A battery pack of Example 12 was formed by aligning the batteries 3 while leaving an interval t of 5 mm from one battery 3 to another battery 3 as are shown in
A battery pack of Example 13 was formed by aligning the batteries 3 while leaving an interval t of 5 mm from one battery 3 to another battery 3 as is shown in
A battery pack of Comparative Example 1 was formed by aligning the batteries 3 while leaving an interval t of 5 mm from one battery 3 to another battery 3 as is shown in
Evaluations as follows were made on the respective battery packs obtained by Examples and Comparative Example above.
The completed battery packs were charged to 25.2 V. Thereafter, a nail made of iron and having a diameter of 2 mm was inserted into a through-hole for nail penetration provided in advance in the battery pack lid at a temperature 20° C. and at a rate of 5 mm per second so that the nail penetrated through the first battery in the battery pack by passing the center portion in the height direction and in the diameter direction. Then, observation was made as to whether a hot inflammable gas discharged from the battery in which nail was inserted burned within the battery pack and other batteries in which no nails were inserted underwent thermorunaway. Also, at the same time, the surface temperatures of the second and sixth batteries were measured in order to determine the heat affect. The through hole for nail penetration was formed in such a manner so as to prevent leakage of an internal gas with a heat resistant sealing member.
The nail penetration test was conducted for Examples 1 through 13 and Comparative Example 1 above and the peak values of the temperatures measured at the position B and C are set forth in Table 1 below. In a state before the nail penetration test was conducted, the temperature of each battery was 20° C., which is equal to ambient temperature. The peak values of the temperatures measured at the positions B and C do not indicate pure battery surface temperatures alone and a temperature rise caused by a hot inflammable gas is added to the peak values.
The term, “thermorunaway”, in Table 1 above indicates a state in which the positive active material in the battery undergoes a reduction action by heat and releases oxygen. When thermorunaway occurs, oxygen released by the reduction reaction burns by reacting with an evaporated electrolyte. The occurrence of thermorunaway was determined by comparing the weights before and after the nail penetration test for each battery 3. In short, it was determined that thermorunaway had occurred when there was a weight loss after the nail penetration test.
As set forth in Table 1 above, it is understood that influences on other batteries can be reduced considerably by reducing a space within the battery pack by one way or another. This is because a hot inflammable gas discharged from the battery is discharged intact to the outside of the battery pack without shifting to a combustion state due to insufficient oxygen within the battery pack.
Also, it is understood from Examples 6 through 8 that even when a space within the battery pack is large, the effect can be achieved by providing the opening with the structure to prevent air from flowing inside from the outside. In this case, the battery temperature becomes slightly higher due to oxygen within the battery pack. However, because oxygen is not supplied from the outside of the battery pack, combustion will not last. Hence, it can be said that influences on the other batteries can be reduced.
However, in the battery pack (Comparative Example 1) having a large spatial volume within the battery pack and having no air inflow prevention means, it is thought that thermorunaway of other batteries was triggered because a hot inflammable gas discharged from the battery shifted to a combustion state due to oxygen in air within the battery pack and the combustion lasted due to air kept flowing inside from the outside. As has been described, it is possible to suppress a hot inflammable gas discharged from the battery from continuing to burn within the battery pack by reducing a space within the battery pack to the smallest possible extent and by providing the inflow preventing structure that prevents air from flowing inside from the outside. It thus becomes possible to lessen damage on the battery pack and spread of fire.
A personal computer, which is an example of a battery-mounted device according to the second embodiment of the invention will now be described.
An electric tool as an example of the battery-mounted device according to the third embodiment of the invention will now be described.
An automobile, which is an example of a battery-mounted device according to the fourth embodiment will now be described.
The tubular member 6 is provided in such a manner that one end is connected to the battery accommodation chamber 21 and the other end opens to the outside of the automobile. The nonflammable gas tank 71 stores, for example, a compressed nonflammable gas (inert gas). The battery accommodation chamber 21 and the nonflammable gas tank 71 are connected to each other with the tube 73. The safety valve 72 is provided to the opening of the tube 73 on the side of the battery accommodation chamber 21.
The safety valve 72 is configured in such a manner that the valve opens, for example, when it is heated to or above a predetermined temperature. According to the foregoing structure, when an abnormality occurs in the assembled battery 31 and the safety valve 72 is heated to or above the predetermined temperature, the safety valve 72 opens for the nonflammable gas to be supplied inside the battery accommodation chamber 21 from the nonflammable gas tank 71. Accordingly, the nonflammable gas supplied from the nonflammable gas tank 71 forces out a gas released from the assembled battery 31 and oxygen within the battery accommodation chamber 21 to the outside of the battery accommodation chamber 21 and further to the outside of the automobile via the tubular member 6. It thus becomes possible to lower a risk that a gas released from the assembled battery 31 burns within the battery accommodation chamber 21.
With this structure, it is possible to achieve the same effect as achieved from the above explained first embodiment.
It should be appreciated that the oxygen reducing portion is not limited to a valve that opens when heated. For example, the oxygen reducing portion may be a control circuit that opens the safety valve 72 upon detection of an abnormality in a battery 3 on the basis of the temperature or a voltage across the battery 3, an internal pressure of the battery accommodation chamber 21.
A battery pack according to one aspect of the present invention includes a battery having a risk of releasing a gas under abnormal conditions, a case that accommodates the battery, and an oxygen reducing portion that reduces an amount of oxygen within the case.
According to the foregoing structure, an amount of oxygen within the case is reduced by the oxygen reducing portion. Hence, should a gas be released from the battery, it is possible to lessen damage on the battery pack caused by combustion of the gas within the case because an amount of oxygen to react with the gas has been reduced.
Also, it is preferable that the oxygen reducing portion includes a filling member that is provided to fill a space between the case and the battery. With this structure, an amount of oxygen present in a space between the case and the battery is reduced by the filling member. Hence, should a gas be released from the battery, it is possible to lessen damage on the battery pack caused by combustion of the gas within the case because an amount of oxygen to react with the gas has been reduced.
Also, it is preferable that the filling member is a nonflammable material. With this structure, should a gas be released from the battery and oxygen remaining in the space between the case and the battery react with each other to generate heat, it is possible to reduce the spread of damage on the battery pack through the burning of the filling member.
Also, the filling member may be a solid, a liquid, or a gas. When the filling member is a solid, because it is easy to handle, the assembly of the battery pack becomes easier. When the filling member is a liquid, even when the shape of a space between the case and the battery is complex, it is easy to fill the space with the filling member. When the filling member is a gas, it becomes easy to reduce the weight of the battery pack.
Also, the oxygen reducing portion may include an oxygen absorbing member that absorbs oxygen. With this structure, an amount of oxygen within the case is reduced by the oxygen absorbing member. Hence, should a gas be released from the battery, it is possible to lessen damage on the battery pack caused by combustion of the gas within the case because an amount of oxygen to react with the gas has been reduced.
Also, the oxygen reducing portion may include an inert gas releasing member that releases an inert gas inside the case when an internal temperature of the case exceeds a predetermined temperature. With this structure, should the internal temperature of the case exceed the predetermined temperature due to heat generation of the battery or heat generated by a reaction between oxygen remaining in a space between the case and the battery and a gas when the gas is released from the battery, an inert gas is released inside the case by the inert gas releasing member. Hence, should a gas be released from the battery, it is possible to lessen damage on the battery pack caused by combustion of the gas within the case because a reaction between the gas and oxygen is suppressed by the inert gas.
Also, it is preferable to further include a releasing portion that releases a gas released inside the case from the battery to an outside of the case. With this structure, should a gas be released from the battery, it is possible to lessen damage on the battery pack caused by combustion of the gas within the case because the gas is released to the outside of the case by the releasing portion.
Also, it is preferable to further include an inflow prevention portion that prevents air from flowing inside the case from the outside via the releasing portion. With this structure, the inflow prevention portion prevents air from flowing inside the case from the outside. Hence, should a gas be released from the battery, it is possible to lessen damage on the battery pack caused by combustion of the gas within the case due to oxygen flowing inside the case from the outside.
Also, it is preferable that the inflow prevention portion is a pressure valve that prevents air from flowing inside the case and releases the gas released inside the case from the battery to the outside of the case when an internal pressure of the case exceeds a preset pressure. With this structure, the pressure valve prevents air from flowing inside the case from the outside unless an internal pressure of the case exceeds the preset pressure. Hence, should a gas be released from the battery, it is possible to lessen damage on the battery pack caused by combustion of the gas within the case due to oxygen flowing inside the case from the outside. In a case where the internal pressure of the case exceeds the preset pressure, the gas released inside the case from the battery: is released to the outside of the case by the pressure valve. It is therefore possible to suppress the case from exploding due to an increase in the internal pressure of the case.
Also, the inflow prevention portion may be a member that increases airflow resistance by bending a channel of air. With this structure, because airflow resistance is increased because a channel of air flowing into the case from the outside is bent, oxygen in air flowing to the case from the outside is reduced. Hence, should a gas be released from the battery, it is possible to lessen damage on the battery pack caused by combustion of the gas within the case due to oxygen flowing inside the case from the outside.
Also, the inflow prevention portion may be a protrusion provided so as to protrude into a channel of air from the outside to inside the case. With this structure, because airflow resistance of air flowing into the case from the outside is increased by the protrusion provided so as to protrude inside the channel, oxygen in air flowing to the case from the outside is reduced. Hence, should a gas be released from the battery, it is possible to lessen damage on the battery pack caused by combustion of the gas within the case due to oxygen flowing inside the case from the outside.
Also, it is preferable that the battery further includes a releasing opening through which the gas is released when an internal pressure of the battery rises, and that the battery pack further includes a tubular member that guides the gas released through the releasing opening to the releasing portion. With this structure, when a gas is released through the releasing opening when the internal pressure of the battery rises, the released gas is guided to the releasing portion by the tubular member and released to the outside. Hence, it is possible to lower a risk that damage is given to the battery by the gas that diffuses on the periphery of the battery and burns in vicinity of the battery.
Also, the case may be formed using a material that absorbs oxygen so as to function as the oxygen reducing portion. With this structure, an amount of oxygen within the case is reduced by the case. Hence, should a gas be released from the battery, it is possible to lessen damage on the battery pack caused by combustion of the gas within the case because an amount of oxygen to react with the gas has been reduced.
Also, the case may be formed by using a material that releases an inert gas inside the case when an internal temperature of the case exceeds a predetermined temperature so as to function as the oxygen reducing portion. With this structure, should the internal temperature of the case exceed the predetermined temperature due to heat generation of the battery or heat generated by a reaction between oxygen remaining in a space between the case and the battery and a gas when the gas is released from the battery, an inert gas is released inside the case by the case. Hence, should a gas be released from the battery, it is possible to lessen damage on the battery pack caused by combustion of the gas within the case because a reaction between the gas and oxygen is suppressed by the inert gas.
Also, a battery-mounted device according to another aspect of the invention includes the battery pack described above. With this structure, it is possible to lessen damage on the battery pack caused by combustion of the gas within the case of the battery pack mounted on the battery-mounted device.
Also, the battery-mounted device according to one aspect of the invention includes a battery having a risk of releasing a gas under abnormal conditions, an accommodation chamber that accommodates the battery, and an oxygen reducing portion that reduces an amount of oxygen within the accommodation chamber. With this structure, an amount of oxygen within the accommodation chamber in which is accommodated the battery having a risk of releasing a gas is reduced by the oxygen reducing portion incorporated in the battery-mounted device. Hence, should a gas be released from the battery, it is possible to lower a risk that the battery and the battery-mounted device are damaged by combustion of the gas within the accommodation chamber because an amount of oxygen to react with the gas has been reduced.
Also, it is preferable that the oxygen reducing portion includes an oxygen absorbing member that absorbs oxygen. With this structure, an amount of oxygen within the accommodation chamber is reduced by the oxygen reducing portion. Hence, should a gas be released from the battery, it is possible to lessen damage on the battery-mount device caused by combustion of the gas within the accommodation chamber because an amount of oxygen to react with the gas has been reduced.
Also, the oxygen reducing portion may include an inert gas releasing member that releases an inert gas inside the accommodation chamber when an internal temperature of the accommodation chamber exceeds a predetermined temperature. With this structure, should the internal temperature of the accommodation chamber exceed the predetermined temperature due to heat generation of the battery or heat generated by a reaction between oxygen remaining in a space of the accommodation chamber and a gas when the gas is released from the battery, an inert gas is released inside the accommodation chamber by the inert gas releasing member. Hence, should a gas be released from the battery, it is possible to lessen damage on the battery-mounted device caused by combustion of the gas within the accommodation chamber because a reaction between the gas and oxygen is suppressed by the inert gas.
Also, it is preferable to further include a releasing portion that releases a gas released inside the accommodation chamber from the battery to an outside of the accommodation chamber. With this structure, should a gas be reduced from the battery, the gas is released to the outside of the accommodation chamber by the releasing portion. It is therefore possible to lessen damage on the battery-mount device caused by combustion of the gas within the accommodation chamber.
Also, it is preferable to further include an inflow prevention portion that prevents air from flowing inside the accommodation chamber from the outside via the releasing portion. With this structure, the inflow prevention portion prevents air from flowing inside the accommodation chamber from the outside. Hence, should a gas be released from the battery, it is possible to lessen damage on the battery-mounted device caused by combustion of the gas within the accommodation chamber due to oxygen flowing inside the accommodation chamber from the outside.
Also, it is preferable that the inflow prevention portion is a pressure valve that prevents air from flowing inside the accommodation chamber and releases the gas released inside the accommodation chamber from the battery to the outside of the accommodation chamber when an internal pressure of the accommodation chamber exceeds a preset pressure. With this structure, the pressure valve prevents air from flowing inside the accommodation chamber from the outside unless the internal pressure of the accommodation chamber exceeds the preset pressure. Hence, should a gas be released from the battery, it is possible to lessen damage on the battery-mounted device caused by combustion of the gas within the accommodation chamber due to oxygen flowing inside the accommodation chamber from the outside. In a case where the internal pressure of the accommodation chamber exceeds the preset pressure, the gas released inside the accommodation chamber from the battery is released to the outside of the accommodation chamber by the pressure valve. It is therefore possible to suppress damage on the battery-mounted device caused by an increase in the internal pressure of the accommodation chamber.
Also, the inflow prevention portion may be a member that increases airflow resistance by bending a channel of air. With this structure, because airflow resistance is increased by bending a channel of air flowing inside the accommodation chamber from the outside, oxygen in air flowing inside the accommodation chamber from the outside is reduced. Hence, should a gas be released from the battery, it is possible to lessen damage on the battery-mounted device caused by combustion of the gas within the accommodation chamber due to oxygen flowing inside the accommodation chamber from the outside.
Also, the inflow prevention portion may be a protrusion provided so as to protrude into a channel of air from the outside to inside of the accommodation chamber. With this structure, because airflow resistance of air flowing into the chamber from the outside is increased by the protrusion provided so as to protrude into the channel, oxygen in air flowing into the accommodation chamber from the outside is reduced. Hence, should a gas be released from the battery, it is possible to lessen damage on the battery-mounted device caused by combustion of the gas within the accommodation chamber due to oxygen flowing inside the accommodation chamber from the outside.
Also, it is preferable that the battery further includes a releasing opening through which the gas is released when an internal pressure of the battery rises, and that the battery-mounted device further includes a tubular member that guides the gas released through the releasing opening to the releasing portion. With this structure, when a gas is released through the releasing opening as the internal pressure of the battery rises, the released gas is guided to the releasing portion by the tubular member and released to the outside. It is therefore possible to lower a risk that the battery-mounted device is damaged by the gas that diffuses on the periphery of the battery and burns in vicinity of the battery.
Also, it is preferable that the inert gas releasing member is formed by using a material that releases an inert gas inside the accommodation chamber when an internal temperature of the accommodation chamber exceeds a predetermined temperature. With this structure, should the internal temperature of the accommodation chamber exceed the predetermined temperature due to heat generation of the battery or heat generated by a reaction between oxygen remaining in the accommodation chamber and a gas when the gas is released from the battery, an inert gas is released inside the accommodation chamber by the inert gas releasing member. Hence, should a gas be released from the battery, it is possible to lessen damage on the battery-mounted device caused by combustion of the gas within the accommodation chamber because a reaction between the gas and oxygen is suppressed by the inert gas.
The battery pack of the invention is able to lessen damage on the battery pack and spread of fire even when a hot inflammable gas is discharged from a battery within the battery pack upon occurrence of an abnormality in the battery and is also able to lower a risk that fire spreads outside the battery pack.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2006-280134 | Oct 2006 | JP | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/JP2007/068057 | 9/18/2007 | WO | 00 | 3/31/2009 |
